1. Field of the Invention
The present invention relates in general to printer systems, and more particularly to printer systems for printing electric circuit patterns on an insulating base board. More specifically, the present invention is concerned with printer systems of a type which generally comprises a printer device of so-called "screen print type" which prints on an insulating base board an electric circuit through a screen plate, a screen plate cleaning device which cleans the screen plate and an ink supplier which feeds the printer device with viscous inductive ink.
2. Description of the Prior Art
Hitherto, various types of printer systems have been proposed and put into practical use particularly in the field of printed circuit manufacture. Some of them are of a type which employ a so-called "screen print type printer". This type printer device comprises, generally, a screen plate, which is set on an insulating base board to be printed, and an ink squeegeeing device which runs on the screen plate, while squeegeeing a given amount of viscous conductive ink onto the screen plate and pressing the same against the insulating base board. With this, on the surface of the insulating base board, there is printed a desired circuit pattern of the conductive ink, which coincides with a perforated print pattern formed in the screen plate. The base board is then heated for fixing the printed circuit pattern. The screen plate is usually constructed of a stainless steel, silk or the like.
For clarifying the present invention, some of conventional printer systems using the screen print type printer device will be described in brief.
Japanese Patent Application 2-419135 shows an ink squeegeeing device usable in such printer devices. The ink squeegeeing device comprises generally a pair (viz., front and rear) of metal blades which have lower ends contactable with an upper surface of the screen plate, an ink container housing which is located between the paired blades and has an ink outlet opening through which a viscous conductive ink in the housing is squeegeed toward the blades, and a shutter mechanism which opens the ink outlet opening when printing is needed and closes the opening when not needed. Only when the ink container housing is advanced for carrying out printing, the lower ends of the paired blades are brought into contact with the upper surface of the screen plate and one of the blades, which is the trailing one, serves as a squeegeeing blade. However, due to inherent construction, the printer device of the application has some drawbacks which are as follows. First, due to the repeated frictional contact carried out between the metal blades and the screen plate, one or both of them tend to have a marked abrasion within a shorter time, which thus shortens their lifetime. Their lifetime is further shortened when the ink contains pewter particles. In fact, during printing operation, the pewter particles get into a space between the blade tips and the screen plate, and thus abrade them. In order to solve this drawback, a measure has been hitherto proposed in which plastic blades are used in place of the conventionally used metal blades. However, in this measure, due to the nature of the plastic which is the material of the blades, it is difficult to press the tips of the blades against the screen plate with a satisfactory pressing force. By this reason, the pewter particles in the ink tend to separate from the flux of the ink during movement of the blades on the screen plate, resulting in the pewter particles being left in the perforations of the screen plate thereby lowering the printing quality of the printer device. Of course, in order to obtain a satisfactory pressing force with which the blades are pressed against the screen plate, another measure may be thought out in which both the screen plate and the blades are constructed thicker in size. However, in this case, it becomes very difficult to form the screen plate with a very fine perforated print pattern. Furthermore, if the blade pressing force is extremely high, the perforations of the screen plate are easily deformed and finally broken. Furthermore, the printer device fails to provide the squeegeeing blade with a stable squeegeeing operation. In fact, during movement of the squeegeeing blade on the screen plate, the pressing force of the blade against the screen plate fluctuates markedly, which lowers the printing quality.
Japanese Patent Application 2-419135, as mentioned hereinabove, and Japanese Utility Model Application 3-77831 show a roller installed in the ink container housing of the printer, which has two functions, one being to stir up the viscous ink in the ink container housing when the ink outlet opening is closed and the other being to press out the ink when the ink outlet opening is open. However, repeated experiments and tests have revealed that a satisfactory stirring of the ink is not obtained from such roller particularly when the viscosity of the ink is high. In fact, when treating such highly viscous ink, the stirring effect on the ink at a distance from the rotating roller is quite low.
Some Japanese Patents and Patent Provisional Publications show a screen plate cleaning device for cleaning the screen plate, which functions to remove residual ink left on the screen plate. Some are of a one-way trip type, in which sweeping action is carried out once per each cleaning, and some are of a round trip type, in which the sweeping action is carried out twice. However, due to the nature of the residual ink, the cleaning devices of these types fail to exhibit a satisfactory cleaning performance.
Other Japanese Patents and Patent Provisional Publications show an open type ink containing chamber defined by the ink container housing. That is, the chamber is constructed to be exposed to the open air. However, in this case, the ink in the chamber is easily affected by the surrounding air. In fact, under such open condition, the ink easily loses volatile components and thus the viscosity of the ink changes or increases instantly. Furthermore, the ink is easily oxidized, which changes the nature of the ink.
Other Japanese Patents and Patent Provisional Publications show an ink supplier which feeds the printer device with viscous ink. However, due to inherent constructions, the ink suppliers shown by such documents fail to exhibit a satisfactory ink supplying performance.